Centrifugal switch



No 7, 1950 c. E. SPRAGUE 2,5

CENTRIFUGAL SWITCH 2 Sheets-Sheet 1 Filed Sept. 29, 1947 TTU /VEW Nov.7, 1950 -c. E. SPRAGUE 2,528,845

' CEN'I'RIF'UGAL SWITCH Filed Sept. 29, 1947 2 Sheets-Sheet 2//\/A/E/\/7'UFE' w. CHESTER E. SPRAGUE' )4 i- TERA/E Patented Nov. 7,1950 UNITED STATES PATENT OFFICE CENTRIFUGAL SWITCH Chester E. Sprague,Portland, Oreg.

Application September 29, 1947, Serial No. 776,660

I 4 Claims. 1

This invention relates generally to electric switches and particularlyto electric switches of the type adapted to be actuated by an operatorresponsive to the direction and rate of rotation of the operator aboutan axis.

Attention is called to my United States Patent No. 2,382,827 coveringsome of my earlier work in this field.

It is the principal object of this invention to provide an improved typeof combined selector and starting switch to be used in connection withthe starting winding of a split-phase electric motor and to bediscriminatingly operated by an actuator carried on the rotor of themotor.

A second object is to provide such a switch requiring only a limitedspace and which will be both reliable in operation and inexpensive toproduce.

I accomplish these and other objects in the manner set forth in thefollowing specification as illustrated in the accompanying drawings, inwhich:

Fig. 1 shows a side view of a typical split-phase motor with the motorframe partially broken away to show my switch and switch operator inplace.

Fig. 2 is a face view of a common type of centrifugal operator for asplit-phase motor starting switch.

Fig. 3 is a wiring diagram showing how the windings of a split-phasemotor are connected to a power source with my improved internal switchand an external controller.

Fig. 4 is a section along the line 4-4 of Fig. 2 and together with Fig.2 shows the relation of the parts of the centrifugal operator when themotor is at rest.

Fig. 5 is a face view of the centrifugal operator showing the parts inexpanded position as when the motor is operating above a pre-set speed.

Fig. 6 is a face view of my switch showing the relation of the partswhen the motor is not running.

Fig. '7 is a face view of my switch showing the relation of the partswhen the motor is rotating in one direction.

Fig. 8 is a face view of my switch showing the relation of the partswhen the motor is rotating in the other direction.

Fig. 9 is a side view in partial section of my switch as shown in Fig.6.

Similar numerals refer to similar parts throughout the several views.

Referring to Fig. 1, at H is shown a motor stator with one end bell l2cut away to show one end bearing support with bearing liners |3supporting a shaft l4 on which is pressed a rotor I5 to which concentricwith shaft I4 is mounted centrifugal switch operator base member I6 bymeans of machine screws l1. Mounted on the inside of end bell l2 bymeans of bolts I8 is insulated base plate [9 of my internal switch. Itis to be noted that the centrifugal switch operator rotates with themotor rotor and that my internal switch mounts on the inside of the endbell of the motor and does not rotate with the rotor.

Figs. 2, 4, and 5 show a common type of switch operator which iscombined in my invention and is shown and will be briefly describedbecause my internal switch is particularly adapted to be used with sucha switch operator and an understanding of the cooperation of my switchwith this type of operator is essential to the understanding of myinvention. On base member l6 of the switch operator are pivoted by meansof headed and shouldered screws 20 three equally spaced crescent-shapedflying members 2| each of which has fixed to it a, weighting member 22by means of rivets 23. Turned up on base member "S are three-equallyspaced ears 24 each perforated to receive a hooked end of one of threetension springs 25. Each flying member 2| is offset as at 2B and in theoffsetting portion is perforated to receive the other hooked end of oneof the springs 25. The design of springs 25 isso balanced with thedesign of the weights 22 and flying members 2| that at about two-thirdsfull speed of the motor rotor, the centrifugal force of the flyingmembers overcomes the closing force of the springs and the positions ofthe parts suddenly change from the lower speed positions of Fig. 2 tothe higher speed positions of Fig. 5. The construction, not particularlyillustrated, is such that there are definite inner and outer limits tothe motions of the members 2|.

Figs. 6, 7, 8, and 9 show a preferred construction of the internalswitch of my invention which switch combines the function of a so-calledstarting switch with the special selector switch function of myinvention. Mounted on insulating base plate I!) by screws 2'! arestationary contacts 28 and 29 to which are attached respectivelyconducting wires 30 and 3| by means of terminal screws 32 and 33. Spacedfrom base plate I9 is metal switch plate 34. Near the top of switchplate 34 and secured to its back by screws 35 is insulator 36 to whichresilient spring arm 31 is flexibly mounted at its mid-point by pin 38.Mounted respectively on the ends of spring arm 3 31 are contacts 39 and40. Also connected to spring arm 31 by pin 38 is conductor 4|.

Switch plate 34 on its vertical center line is perforated to form radialslot 52 near its lower end and inverted V-shaped slot 43 near its upperend. Also switch plate 34 is perforated nea its center to form largeshaft clearance hole 44. Formed to stand forwardly on switch plate 3 8are operating ears 45 and 46 which, as shown in Fig. 1, are mounted inthe plane of action of, and straddling, flying members 2! of thecentrifugal switch operator.

Shown on Figs. 6, '7, and 8 are broken line circles showing the innerlimit ll and the outer limit 56 of flying members 2| at the speedconditions shown, Fig. 6 corresponding to Fig. 2, Fig. 7 correspondingto Fig. in one direction, and Fig. 8 corresponding to Fig. 5 in theother direction of rotation of shaft [4.

Switch plate 55 is pivotally supported on base plate l5 by headed andshouldered bolt 5-9 and spaced from base plate is by spacer 5|]. Switchplate 35 is guided in its movement under the action of flying members 2|by headed and shouldered bolt 5| fixed in base plate [5. Bolts 49 and 5|penetrate switch plate 35 through slots 42 and 53 respectively.

Referring to Fig. 3, broken circle 52 includes generally my internalswitch and operator described above. Small circles 55, 5Q, 55, 56, 5i,58, 59, and 66 represent the insulated stationary contacts of acontroller external to the motor of Fig. l of which 6| represents thestarting winding, and 62 represents the running winding. Controlledrotor contact bridging bars 63 and 6 3, shown in the neutral or offposition of the controller, are shown connected to electric supply lines65 and 66 respectively. Conductor 'il connects to one end of startingwinding 6|, the other end of which is connected to contacts 53 and 55 byconductor 6'1. Running winding is connected at one end to contacts 56and 5'! by conductor 63 and at the other end to contacts 55 and 58 byconductor 69. Conductors 35 and 3| connect to contacts 59 and 65respectively.

To further explain my invention, assume that a split phase motor isequipped with my internal switch and operator as above described and isconnected to a suitable power source through a simple drum controlleraccording to the diagram of Fig. 3. With the controller in the neutralposition shown, no movement of the motor occurs. Now assume that thecontroller handle (not shown) is pressed to the right so that controllerbar 63 bridges contacts 54 and 56 and connects them with power line 65.Similarly, controller bar 66 bridges contacts 58 and 66 and connectsthem to power line 66. Assume now that current flows through the motorsystem from power line 65 to power line 66. It is seen that currenttraverses the motor running winding in the direction of elementsnumbered 65, 63, 56, 57, 68, 62, 55, 53, 65, and 66. Current willtraverse the starting winding in the direction of elements numbered 65,63, 54, 6?, 6|, 5|, 37, ill, 29, 3|, 60, 64 and 66. Since both windingsare energized, the motor will start in the direction determined by thephysical arrangement of the winding. Let us assume it starts to rotatein a counter-clockwise direction. In a very short time the motor willattain approximately two-thirds of its full speed and the flying membersof the internal switch operator suddenly fly outward or from theposition of Fig. 3 to the position of Fig. 5. As this occurs, the flyingmembers of the operator exert a quickly applied radial force and africtionally applied tangential force on operating ear 4 of the internalswitch, thus throwing the internal switch quickly from the position ofFig. 6 to that of Fig. 8, thus disconnecting contact 40 of switch arm 31from stationary contact 29 but leaving contact 39 of switch arm 3'! fromstationary contact 28. It should be noted that as the flying members ofthe operator react on operating ear 46 and switch plate 34 is urgedupwardly and to the left, an added flexure is given to spring switch arm31 and the shape and location of inverted V slot 43 is such that switchplate 34 is stable in its new position with switch ear 46 just out ofreach of flying members 2| which, as above noted, have stops to limittheir outward travel. It is seen that the circuit to the startingwinding has been opened and the motor continues to run at rated speed ina counter-clockwise direction.

Now, if the controller handle is returned to neutral position, power iscut oil from the motor and due to the load to which it is applied or toits own friction and windage or both the motor slows down and stops.While it is slowing down, at about two-thirds speed, springs 25 overcomethe centrifugal force on members 2| and 22 and the flying members returnto their rest positions. In doing this, they contact operating ear 45and in further closing they overcome the forces holding the switch platein the position of Fig. 8 and the switch plate returns to the positionof Fig. 6 with contacts 29 and ll] aga n in contact.

Now, if the controller handle is pressed to the left so that controllerbar 63 bridges contacts 53 and 56 and controller bar 64 bridges contacts5'! and 59, it is seen that current will traverse the starting windingin the same direction as before but the direction of current flowthrough the running winding is reversed and the motor starts up in theopposite or clockwise direction. This time in attaining abouttwo-thirds, speed the flying members will again suddenly spread out andexert a quick radial force on operating car 46 but the tangential forcewill be clockwise so that while the operator changes from the positionof, Fig. 2 to the posit on of Fig. 5 the switch plate will change fromthe position of Fig. 6 to the position of Fig. '7.

It is thus seen that with my invention, the motor can be operated fromrest to either direction of rotation. But the great advantage of myinvention is that with it when the motor is running in one direction aquick reversal of the controller will just as quickly reverse thedirection of current flow through the running winding and thus add thefull magnetic reaction of the motor windings to the normal load reactionto bring the motor to a quick and complete stop. And if the controlleris not returned to neutral position when the motor stops, it willimmediately start up in the reverse direction. It is this ability toreverse the current reaction to quickly stop the motor and, if desired,to start the motor in the opposite d rection which is the principalfunctional object of this invention, as well as of my previous patentabove noted. Above is fully described the circuit and mechanisms of thisinvention which attain this object.

I am aware that changes could be made to mechanisms shown withoutdeparting from the general design of my invention and, therefore, whileI make no claim to every means for accomplishing the functions of myinvention, I do intend to reserve to myself the full compass of thosevariations of mechanisms and circuit which come within the spirit of myinvention.

I claim:

1. In combination with a rotatable centrifugal switch operator, havingradially flying members biased to a position of lesser radius butmovable under the influence of centrifugal force to a position ofgreater radius, of a combined selector and centrifugal starting switchfor a split-phase motor, comprising a plate having a center hole looselysurrounding the shaft of said motor, said plate being perforated with aslot radial of said motor shaft and at one side of said shaft and saidhole, said plate being perforated with a V shaped slot pointing awayfrom said shaft and at the opposite side of said shaft and said hole, afirst fixed pin extending through said radial slot and pivoting saidplate, a second fixed pin extending through said V shaped slot andguiding said plate as it slides along and pivots on said first pin insaid radial slot, a first stationary contact spaced from said plate, asecond stationary contact spaced from said plate, resilient meanscarried by said plate and carrying movable contacts for cooperating withsaid first and said second contacts, and means carried by said plate forem gaging said switch operator whereby when said switch operator flyingmembers are in their position of lesser radius said first and saidsecond contacts will each be engaged by its cooperating movable contactand when said switch operator flying members are in their position ofgreater radius in one direction of rotation only the first stationarycontact will be engaged by its cooperating movable contact and when saidswitch operator flying members are in their position of greater radiusin the other direction of rotation only the second stationary contactwill be engaged by its cooperating movable contact.

2. In combination with a rotatable centrifugal switch operator havingflying members movable in a plane normal to the axis of rotation andbiased to a position of lesser radius below a preset speed, anon-rotating combined selector and starting switch for a split-phasemotor comprising a first single pole switch having a fixed contact and amovable contact, a second single pole switch having a fixed contact anda movable contact, and intermediate means movable only in a plane normalto the axis of rotation for engaging said flying members and throwingsaid switches, whereby below a pre-set speed of said operator in eitherdirection both of said switches will be closed and above said pre-setspeed in one direction only one of said switches Will be closed whileabove said pre-set speed in the other'direction only the other of'saidswitches will be closed.

3. A combined selector and starting switch for a reversible split-phasemotor comprising a plate fixed in a plane normal to the shaft of saidmotor and having a center line, two spaced pins fixed to said plate onsaid center line and parallel to said shaft, a movable plate parallel tosaid fixed plate, said movable plate being perforated to form andelongated slot and a spaced V-shaped slot, said pins guidingly engagingsaid movable plate in said slots, two spaced insulated contacts carriedby said fixed plate, two spaced movable contacts carried by a resilientmember rockably carried by said movable plate, and two spaced operatingmembers fixed normal to said movable plate.

'4. A combined selector and centrifugal starting switch for asplit-phase motor comprising a plate having a center hole looselysurrounding the shaft of said motor, said plate being perforated to forma vertical slot below said hole and an inverted V-shaped slot abovesaidhole, a first fixed pin extending axially of said motor through saidvertical slot, a second fixed pin extending axially of said motorthrough said V-shaped slot, fixed abutting means at each side of saidplate and spaced therefrom, and resilient means carried by said plateand cooperating with said abutting means, whereby when said plate ismoved to position said second pin at the apex or at either end of theV-shaped slot said plate will be stable in that position.

CHESTER E. SPRAGUE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITEDVSTATES PATENTS Number Name Date 771,269 Reist Oct. 4, 19042,382,827 Sprague Aug. 14, 1945 2,389,381 McLennan Nov. 20, 19452,406,430 Mason Aug. 27, 1946

